Method for converting asbestos to non-carcinogenic compounds

Abstract

Hazardous and carcinogenic asbestos waste characterized by a crystalline fibrous structure is transformed into non-carcinogenic, relatively nonhazardous, and non-crystalline solid compounds and gaseous compounds which have commercial utilization. The asbestos waste is so transformed by the complete fluorination of the crystalline fibrous silicate mineral defining the asbestos.

What is claimed is: 
     
       1. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds, comprising the step of contacting a mass of fibrous asbestos comprising a silicate mineral with a reactant consisting of a sufficient volume of fluorine gas for effecting an exothermic reaction with the silicate mineral in said asbestos that is adequate for fluorinating silicate mineral in said asbestos for converting the silicate mineral to a gaseous silicon-containing compound consisting of SiF 4  and to non-silicon-containing gaseous and solid compounds. 
     
     
       2. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds as claimed in claim 1, wherein the asbestos is chrysotile defined by a magnesium silicate mineral having the general chemical formula of H 4  Mg 3  Si 2  O 9 , or an amphibole defined by a silicate of magnesium, calcium, iron or sodium with a hydroxyl, a silica:oxygen ratio of 4:11, and a fibrous cleavage. 
     
     
       3. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds as claimed in claim 2, wherein the mass of fibrous asbestos is contacted with a volume of fluorine gas in excess of the amount required for fully fluorinating the silicate mineral. 
     
     
       4. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds as claimed in claim 2, wherein the asbestos is the chrysotile, and wherein the fluorination and conversion of the magnesium silicate mineral forms said compounds which comprise SiF 4 , MgF 2 , HF, and said O 2 , and wherein the volume of fluorine adequate to essentially fully fluorinate and convert the magnesium silicate mineral to said compounds is at least sufficient for the fluorination of the magnesium silicate mineral in accordance with the chemical equation: H 4  Mg 3  Si 2  O 9  +9F 2  →2SiF 4  ↑+3MgF 2  +4HF↑+4 1/2O 2  ↑. 
     
     
       5. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds as claimed in claim 4, wherein the mass of fibrous asbestos is contacted with a volume of fluorine in excess of the amount required for fully fluorinating the magnesium silicate mineral in accordance with said chemical equation. 
     
     
       6. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds as claimed in claim 5, wherein the volume of fluorine including the excess of the amount required for fully fluorinating the mass of the magnesium silicate mineral corresponds to a ratio, by weight, of about 1.25 to about 1.45 parts fluorine to 1.0 part of the magnesium silicate mineral. 
     
     
       7. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds as claimed in claim 2, including the steps of separating a stream of the gaseous compounds partially defined by silicon fluoride from any solid compounds, and thereafter separating at least the silicon fluoride from the stream of the separated gaseous compounds by passing the stream of the gaseous compounds through a water scrubber for converting the silicon fluoride to hydrogen fluoride and silicic acid. 
     
     
       8. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic, relatively nonhazardous, and non-crystalline compounds as claimed in claim 2, including the steps of separating a stream of the gaseous compounds partially defined by silicon fluoride from any solid compounds, and thereafter separating at least the silicon fluoride from the stream of the separated gaseous compounds by passing the stream of the gaseous compounds through a sodium hydroxide scrubber for converting the silicon fluoride to sodium fluoride and sodium silicate. 
     
     
       9. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds, said method consisting essentially of the steps of confining a mass of asbestos comprising a silicate mineral in an enclosed volume, evacuating the enclosed volume to an absolute pressure adequate to remove substantially all oxygen-containing gases and free water from the enclosed volume, introducing a stream of fluorine gas into the evacuated volume in an amount at least sufficient to exothermically react with the silicate mineral in said asbestos and effect essentially full fluorination of the silicate mineral for the conversion of the silicate mineral to the non-carcinogenic and relatively nonhazardous gaseous and solid compounds defined by a silicon-containing gaseous compound consisting of SiF 4  and non-silicon-containing gaseous and solid compounds, removing the gaseous compounds from the enclosed volume, and thereafter removing the solid compounds from the enclosed volume. 
     
     
       10. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 9, wherein mass of asbestos confined in the enclosed volume is chrysotile defined by a magnesium silicate mineral having the general chemical formula of H 4  Mg 3  Si 2  O 9 , or an amphibole defined by a silicate of magnesium, calcium, iron or sodium with a hydroxyl, a silica: oxygen ratio of 4:11, and a fibrous cleavage. 
     
     
       11. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 10, wherein the asbestos is the chrysotile, and wherein the fluorination and conversion of the magnesium silicate mineral forms the compounds including said SiF 4  and MgF 2 , HF, and O 2 , and wherein the volume of fluorine adequate to essentially fully fluorinate and convert the magnesium silicate mineral to said compounds is at least sufficient for the fluorination of the magnesium silicate mineral in accordance with the chemical equation: H 4  Mg 3  Si 2  O 9  +9F 2  →2SiF 4  ↑+3MgF 2  +4HF↑+4 1/2O 2  ↑. 
     
     
       12. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 9, wherein the amount of fluorine in said stream thereof introduced into the enclosed volume corresponds to a ratio, by weight, of at least about 1.25 parts of fluorine to 1.0 part of the silicate mineral. 
     
     
       13. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 9, wherein the amount of fluorine in the stream thereof introduced into the enclosed volume is in excess of the amount required for fully fluorinating the mass of the silicate mineral. 
     
     
       14. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 9, wherein the excess amount of fluorine in said stream thereof introduced into the enclosed volume corresponds to a ratio, by weight, of about 1.25 to about 1.45 parts of fluorine to 1.0 part of the silicate mineral. 
     
     
       15. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 9, including the additional step of sizing the mass of the silicate mineral into pieces in a size range of about 0.5 inch to about 12.0 inches in cross section before the introduction of the mass of asbestos into the enclosed volume. 
     
     
       16. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 9, including the additional step of maintaining the enclosed volume at a maximum temperature in the range of about 400° to 600° F. during the exothermic reaction. 
     
     
       17. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 13, including the steps of connecting the enclosed volume to at least one additional enclosed volume, confining a mass of asbestos in said at least one additional enclosed volume, introducing said excess amount of fluorine into at least the first mentioned enclosed volume, conveying from the first mentioned enclosed volume into said at least one additional enclosed volume the gaseous compounds produced by the essentially full fluorination of the silicate mineral in the first mentioned enclosed volume, conveying into said at least one additional enclosed volume excess fluorine remaining in the first mentioned enclosed volume from the essentially full fluorination of the silicate material, and introducing a stream of fluorine into said at least one additional enclosed volume in an amount at least sufficient to combine with the excess fluorine from the first mentioned enclosed volume and essentially fully fluorinate the silicate mineral in said at least one additional enclosed volume. 
     
     
       18. A method for transforming asbestos comprising a silicate mineral in a crystalline fibrous form from a carcinogenic and hazardous material to non-carcinogenic and relatively nonhazardous compounds as claimed in claim 17, wherein a plurality of enclosed volumes are serially connected together, and wherein excess fluorine and said gaseous compounds are cascaded through the serially connected enclosed volumes.